An object is to provide a light source unit that focuses a laser beam having different divergence angles in longitudinal direction and lateral direction, without deviating longitudinally and laterally from an incident end-face of an optical fiber, and also that simplifies assembling lenses into a lens barrel. The light source unit herein provided includes a first lens barrel 1 that holds cylindrical lenses 10 and 11, and 12 for forming a parallel-ray laser beam by refracting the laser beam 9 having different divergence angles in longitudinal direction and lateral direction emitted from a laser element 7, a second lens barrel 2 that holds circular lenses 13 and 14 for focusing the parallel-ray laser beam onto the entrance of the optical fiber 3, and a lens holder 15 that holds at least one of the cylindrical lenses and is inserted into the first lens barrel 1 and fixed therein.